1. Field of the Invention
This invention relates generally to fastener retainers and, more particularly, to assemblies for captivating a fastener within a workpiece.
2. Discussion
Manufacturers are constantly striving to increase productivity by reducing assembly time during the manufacturing process. It is known in the art to streamline manufacturing by pre-attaching the fasteners to structural members which are later used in the assembly of a component.
Some representative examples of prior art techniques for captivating fasteners on a workpiece include U.S. Pat. Nos. 5,199,152 and 5,154,559. These patents generally disclose the use of wings or protuberances on the fastener shank. The workpiece is formed with a radially inwardly projecting shoulder portion in its bore. The diameter of the fastener wings is slightly larger than the inner diameter formed by the bore shoulder such that the fastener can be forced through the workpiece so that the shoulder in the bore can still engage the wings of the fastener. U.S. Pat. No. 5,328,111 also requires that the workpiece bore have an area of reduced diameter to maintain a C-shaped clip/fastener preassembly captivated within the workpiece. Another approach is disclosed in U.S. Pat. No. 5,395,194 where a convoluted flexible retainer member serves to captivate the fastener within the workpiece.
Special problems are encountered when the bore of the workpiece is a straight walled polished surface such as the inner bore of a bearing assembly. In such instances the wing/protuberance approaches of the '559 and '152 patents, as well as the design of the '111 patent, is not acceptable because these techniques require that the inner bore of the workpiece be formed with special inwardly projecting portions. In some workpieces, such as bearing assemblies, it is either impractical or undesirable to form such projections within the bore. As will be described later herein, a split-ring retainer member has been employed in an attempt to captivate the fastener within a bearing assembly. However, this technique suffers from several disadvantages. The split-ring is slid over the shank of the fastener and the fastener/split-ring is then press fit into the bore of the bearing assembly. This assembly is then, in turn, press fit into a pulley of a belt tensioner of an accessory drive component for an automobile. This assembly is typically placed into shipping containers with other similar assemblies and then shipped to the final manufacturing plant. Of course, the assemblies tend to experience the usual shaking and jostling during normal shipment. At the plant, the assembly is then mounted to a tapped hole in a bracket in the engine compartment. The worker typically grasps the assembly with one hand and tries to visually align the bolt with the hole in the bracket. Sometimes the worker mis-aligns the bolt with the hole and hits the protruding end of the fastener against the bracket. This force has a tendency to pop-out the fastener (and its split-ring) from the bearing. To some extent, this "pop-out" of the fastener/split ring can occur during shipment as well. In either case, this defeats the purpose of producing the preassembly in the first place.
Therefore, it would be desirable to provide a cost-efficient and effective technique for preassembling a fastener to a workpiece, especially where the workpiece has a very smooth inner bore.